Step 1: Preheat your oven to 350°F (175°C). Grease and flour a 9x5 inch (23x13 cm) loaf pan, or line it with parchment paper, leaving an overhang on the long sides for easy removal.
Step 2: In a medium bowl, whisk together the all-purpose flour, baking powder, baking soda, and salt. Set aside.
Step 3: In a large bowl, combine the granulated sugar and lemon zest. Use your fingers to rub the zest into the sugar for about 1-2 minutes until the sugar is fragrant and moist. This helps release the lemon oils for maximum flavor.
Step 4: Add the eggs, sour cream (or Greek yogurt), vegetable oil, and vanilla extract to the sugar mixture. Whisk until well combined and smooth.
Step 5: Gradually add the dry ingredients from Step 2 to the wet ingredients from Step 4. Mix with a spatula or whisk only until just combined. Be careful not to overmix; a few lumps are okay. Then, stir in the 1/4 cup of fresh lemon juice.
Step 6: Pour the batter into your prepared loaf pan and smooth the top with a spatula. Bake for 50-60 minutes, or until a wooden skewer or toothpick inserted into the center of the loaf comes out clean. If the top browns too quickly, loosely tent the loaf with aluminum foil.
Step 7: Remove the loaf from the oven and let it cool in the pan for 10-15 minutes. Then, carefully lift it out onto a wire rack to cool completely before glazing. This is crucial for the glaze to set properly.
Step 8: While the loaf cools, prepare the glaze: In a small bowl, whisk together the powdered sugar and 3 tablespoons of fresh lemon juice until smooth. The glaze should be thick but pourable. If it's too thick, add a tiny bit more lemon juice; if too thin, add a little more powdered sugar.
Step 9: Once the loaf is completely cool, pour the lemon glaze evenly over the top, letting it drip down the sides. Allow the glaze to set for about 15-20 minutes before slicing and serving. Enjoy your homemade Starbucks Lemon Loaf Recipe!